Poisonous Fog

The Poisonous Fog is the unknown fog that covers the Underground portion of Fortuna HQ, including the laboratory of Agnus. It was known to appear due to the destruction of Bael's Hell Gate after the fight with Dante.

In the game, only Dante was able to sense the poisonous fog after their fight with Bael. This slowly drains his Vitality Gauge, luckily for him, most Cutlass drop Green Orbs here when killed.